(a) Field of the Invention
This invention relates to analgesic pharmaceutical compositions (i.e., compositions for reducing pain) in warm blooded animals. In particular, the invention relates to acetanilide related analgesic compositions.
(b) History of the Prior Art
Historically, there has been a search for methods of reducing pain in warm blooded animals and especially in human beings. The search for a safe, effective analgesic composition, which can be administered to warm blooded animals, has therefore been a continuing one since better safety and effectiveness are always desirable.
One of the most common analgesic compositions for reducing pain is aspirin or sodium acetylsalicylate. Unfortunately, aspirin has some undesirable effects especially in some individuals who are sensitive to aspirin. This sensitivity can take the form of upset stomachs and G.I. disturbances and can be allergic reactions which in uncommon cases can even cause death.
For these reasons, acetaminophen, also known as 4-hydroxyacetanilide, was developed and is marketed as an analgesic for use by those who are sensitive to aspirin. Unfortunately, while acetaminophen seems to cause fewer gastro intestinal disturbances, at least some allergic reactions do occur. Furthermore, the toxicity of acetaminophen is undesirably high and liver damage and even death can result from ingestion of excessive quantities of acetaminophen.
It has been previously known, for example as disclosed in British Pat. No. 1,006,558 that 3-hydroxyacetanilide (m-hydroxyacetanilide, 30H acetanilide) has anti-pyretic activity, (i.e., can reduce fevers). It has not, however, been previously known that 3-hydroxyacetanilide has analgesic properties. 3-hydroxyacetanilide is known to be substantially less hepatotoxic than acetaminophen (see Acetaminophen Structure Toxicity Relationships: Why is 3-hydroxyacetanilide Not Hepatotoxic? Stanley A. Roberts and David J. Jollow. Medical University of South Carolina, Charlston, S.C.)